Gah! I have no idea what the full error message is nor how to fix this issue. I can drag the file (which plays fine in Finder and QuickTime) to the Media Library, but as soon as I attempt to add it to the timeline I get this error and the file is automatically removed from the Media Library. Happened also with the original MP4, which I converted to MOV hoping to remedy the issue.
Any suggestions? I'd like to suggest, though, that Telestream update this dialog to show complete error messages.
v9.0.7, Mac mini (Late 2012), 16GB, 500GB SSD, macOS Catalina 10.15.7.
Try using either Quicktime Player to export as a H.264 (greater compatibility) or Handbrake (make sure you select constant frame rate under video settings) or some other third party encoder.
To do a deeper dive, we would need to have access to your file. If you could create a support ticket then one of our ScreenFlow technicians can work with you to figure out what it is about the file that ScreenFlow is having problems with ( http://www.telestream.net/telestream-support/screen-flow/contact-support.htm ).